The aforementioned related application, which corresponds to European Application Publication No. 0233587, relates to photocurable compositions containing ionic dye complexes as photoinitiators. These complexes are characterized in that they directly or indirectly yield free radicals upon exposure to actinic radiation and particularly visible light.
By nature, compositions which are sensitive to visible light appear colored to the human eye. There are applications in which it would be desirable to use the compositions which can be cured upon exposure to visible light but for the colored appearance of these compositions. For example, in laminating glass, if the composition is colored it imparts a tint to the glass which may be undesirable. Similarly, a visible initiator would be advantageous in coating optical fibers but for its colored appearance. In these applications, photobleachable ionic dye complexes would be particularly useful. In some of the compositions disclosed in the related application, the dye has been observed to be photobleachable.